This. Or just MS Paint.
Pixel Art is simply a matter of zooming in really close, to where one block on your screen is a single pixel, and then creating people.
The #1 thing you need to know, is that all people rely on references.
Find a game with similar art to what you’d like. If there are multiple games with this type of art style, then even better.
Take some screenshots and paste the characters alongside your own.
Using them as references, try to draw something similar.
If it helps, start with something simple but important, like the head.
In the end, even if you use a reference- the art will be yours, with your unique touch, your decisions, your creativity. You will quickly find what you LIKE and what you DISLIKE about the references. You may even combine references.
Trial and Error with reference is also great. My guys are faceless. I tried tons of SNES and NES game sprite eyeballs and faces, and in the end? Nothing was even close to my faceless people, IMO. Eyeballs looked goofy on them. Real goofy.
Except of course, my blob aliens. The eyeballs were ever-so important.
I am not a pixel artist, just an amateur. However, I started with references to create the little guys in my avatar. I used several games, most of which I discarded as references.
My character’s face pixels actually are very important to me, and IMO make a world of difference between the humans (shown in avatar) and aliens (not shown).
The Result after practice using reference? I learned enough to make a blob guy without pixelart reference!
My references? Random google images and some references that had nothing to do with pixel art, but instead gave me an idea of how I want my blob guy to look. I was able to translate the idea into a pixelated guy.

I have about 10 types of species for my game right now, and animation is a breeze once I got the human’s animations down.
Along with those 10 species, I have about 10 other ones I discarded because they looked horrific, or simply not up to par with what I have in the game so far. Along with those discarded pieces, I spent several hours with about 10 different chairs, until I decided upon my pixelated chair. For a ship’s systems, I still do not have it right yet, but have discarded a few. Each time I start over, I get a better result.
Practice. Practice. Practice.
Here is the evolution of my human sprite.

^ First Attempt.
I literally almost gave up immediately . I thought “Wow that is horrible. I suck. I am not an artist. I can’t do this.”
I was on the verge of giving up, and just decided randomly “What the hell, I will try one more time just to see.”

^ Second Attempt
Surprisingly, it was improved enough to give me the confidence to try again. From then on out, I was fully confident I could draw anything (similar to my style) that I needed. I just had to try and spend time on it.

^ Third Attempt
In the end, it actually only took me about 30 minutes to go from a horrific pixel artist (first attempt) to the final attempt. Then only an hour to animate with over 10 animations.

^ Final Attempt
For me at least, Pixel Art is surprisingly easy to learn and easy to do. I am confident that this ease is apparent in everyone as I have no natural artist talent and if I (a non-artist) can do it, I bet others can.
After that, I polished them more and then animated them based on this single idle stance.
However, it would have been significantly harder without all the pixel art references (especially the animations), and even some tips from this link:
http://www.hongkiat.com/blog/pixel-art-tutorials/